1. Field of the Invention
This invention relates to a method and apparatus for moving sheets from substrates without substantially moving the substrate and, specifically, where the sheets are sheets of X-ray film and the substrates are screens found in conventional X-ray cassettes or other sheets in a closely packed stack of sheets.
2. Description of Related Art
Automatic X-ray film handling systems exist that automatically unload exposed sheets of X-ray film from light tight cassettes and reload the light tight cassettes with sheets of unexposed X-ray film, without the need for a darkroom. One such automatic X-ray film handling system is disclosed in U.S. Pat. No. 4,514,958. This system uses conventional suction cups to remove exposed X-ray film from cassettes.
X-ray cassettes are specifically designed to squeeze out air from between the film and an intensifying screen in the cassette in order to enhance radiogram quality. This lack of air between the film and the screen hinders or precludes the easy separation of the film and screen by conventional suction cups.
Due to the vacuum or adhesion between the compressed film and screen, conventional suction cups have a tendency to raise both the film and the screen together. Separation must then be accomplished by sliding the film off the screen. However, many cassettes have obstructions or walls that prevent sliding the film off the screen. An X-ray film cassette is disclosed in U.S. Pat. No. 4,081,686 having a frame which obstructs sliding the film off its screen. This requires the use of special, non-standard, cassettes, such as disclosed in U.S. Pat. No. 4,734,926, in many automatic X-ray film handling systems.
It is an object of this invention to provide a suction cup for raising or curling a portion of a sheet near an edge of the sheet allowing air to enter between the film and the substrate or sheet beneath the sheet desired to be moved.
It is another object of this invention to provide a method and apparatus for separating sheets, such as, of X-ray film, from substrates, such as screens found in conventional X-ray cassettes or other sheets in a closely packed stack of sheets, to break the vacuum between the sheet and substrate and enable the sheet to be removed from the cassette in an acceptable period of time.